Sheet fed scanners have become a popular computer peripheral for creating digital images from documents in both the home and the office. With respect to sheet fed scanners, an image forming subsystem, such as a camera, typically a charged couple device (CCD) and a lens in combination with an illumination source, sits in a stationary position and scans an image as a sheet of paper is moved past the camera, through a narrow transport path, by a paper transport mechanism. Individual raster lines are imaged by the camera and then pieced together to create a two-dimensional (2D) image representation of the original document. The camera is basically imaging one sliver of the document many times as the document is moved past the camera. The paper motion supplies one dimension of the document image, while the width is supplied by the camera. The in-paper travel direction and the width of the document are determined by the optics magnification and the dimensions of the CCD within the image forming subsystem. In alternative designs, a CIS or Contact Image Sensor is substituted for the CCD Lens Reduction form of camera or imager. The CIS device utilizes a number of smaller CCD elements chained together to form a full width imager. This eliminates the need for a reduction lens which is replaced by a self-focusing one of essentially 1:1 magnification. Both forms of cameras or imagers are commonly applied in sheet fed scanners as well as flat bed scanning equipment. In some cases, the shape of the sheet fed scanners paper path is semi-circular. For example, some scanners have a semi-circular paper path wherein sheets can be fed from a tray on top and exit beneath, or vice versa. In other cases, the paper path is “straight through.”
In some cases, the scanner has two cameras, one for imaging the front side of the sheet or document, the other for imaging the rear side of the sheet or document. Scanners of this form are typically referred to as single pass duplex in that they can image both sides of a document with one pass of the document through the paper transport. Sheet fed scanners employing only one imager are generally referred to as Simplex scanners. In some scanners with one imager or camera, the paper path is designed in a way to provide the ability to turn the sheet over thereby allowing for imaging of both sides, but this must be done in a second or reversing pass of the document, with a penalty of increased scan time.
FIG. 1 shows a typical sheet fed scanner with a C-shaped paper path and two cameras for duplex scanning of documents. To scan a stack of documents, a human operator places a stack of documents 10, face up, on elevator input tray 11 and initiates a scan command through an attached computer (not shown) or a button or control panel (not shown) on the scanner. Drive rollers 16 begin to continuously rotate in direction 103. Paper present sensor 17 determines that documents are in elevator input tray 11 and a motor (not shown) raises the tray to position the top of stack 10 against urging roller 13. A motor and/or clutch (not shown) rotate urging rollers 13 and feed rollers 15 to pull the top document from stack 10 and move it into the continuously rotating transport rollers 16 which transport the document through curved transport path (C-shaped) 14 in direction 110.
The documents are imaged by cameras 18 and 19 as they are pulled through the transport path 14. Cameras include one or more illumination sources 196 that illuminate documents to be imaged by an electronic image sensor 192. The image sensor can be a contact image sensor (CIS) or a charge-coupled device (CCD). In the case of a CCD imager, the camera typically includes a lens 198 and one or more mirrors 194 to fold the light path 199 between the imager and the document and create a more compact camera.
Scanned documents 12 are stacked face down in exit tray 20, in the same order as they were fed into the scanner and scanned. When paper edge sensor 101 detects the lead edge of a document, the urging rollers and feed rollers are stopped from rotating to prevent feeding of more than one document. At this point, feed rollers 16 continue to rotate and pull the document through the urging rollers and feed rollers. After the trail edge of the document passes by paper edge sensor 101, the urging rollers 13 and feed rollers 15 are again rotated (by motor and/or clutch not shown) to start moving the next document on the top of stack 10 into transport path 14. In this way, documents are moved one at a time past cameras 18 and 19 to be imaged. Urging roller 13 is mounted to a housing 191 that freely pivots around the axis of the upper feed roller 15, which is attached to the pod portion. Therefore as documents are fed from stack 10, urging roller 13 drops by gravity onto the next document at the top of stack 10. Stack-up sensor 102 detects when urging roller 13 (or its surrounding parts) drops below an optimal range for feeding documents. When this occurs, elevator 11 is raised by a motor (not shown) until stack-up sensor 102 detects that the stack is again in an optimal feeding position.
With reference to FIG. 2, scanners with a C-shaped transport typically have a stationary base portion 122 and a moveable pod portion 120 that is connected by a hinge to the base. The pod can be lifted away from the base on its hinge to allow cleaning of cameras or to remove documents that may become jammed in the transport path. FIG. 2 shows a C-shaped sheet fed scanner with a pod portion 120 attached to a base portion 122 at hinge 124 with the pod in an open position. Such sheet fed designs are referred to as C shaped or “rotary” within the industry.
FIG. 3 shows a typical sheet fed scanner with a straight though paper path and two cameras (duplex) for scanning both sides of documents. Documents 10 are moved through a straight transport path 15 by a series of drive rollers 16 to be imaged by cameras 18 and 19. In this case, documents 10 are pulled from the bottom of the input stack and are stacked 12 in exit tray 20 in the same order. Document stacks must be fed face down in order to scan them in the order in which they are stacked. If a straight through path were to be fed documents in a face up orientation, then the last document in the stack would be the first document scanned. The result would be that the scan order would be reversed from the stack order 12 in the scanner shown in FIG. 3. In applications where many documents are scanned, customer expectations require that the original order be maintained. This is especially important in helping the customers recover from any jam, stoppage or other events that would require starting over or executing a “rescan”.
There are several customer usage benefits to the C or “rotary” design as compared to a straight through sheet fed scanner design. Since many of these advantages deliver improved productivity and improved ergonomics they become much more important in applications where many documents need to be scanned. Within the industry of production scanning where customers expect to scan more than a few tens or few hundreds of documents per day, the rotary or C shaped transport designs are the dominant product configuration. Following are some of the usage benefits of a Rotary or C shaped transport design.
Given the customer requirement to deliver the sheets to an exit tray in the same order as they were scanned, the options are to feed them through a straight path face down using a feeder that pulls the intended sheets into the transport from the bottom of the stack or use a C shaped transport where the sheets can be pulled from the top of stack. Pulling the sheets off of the top of the stack or a “top feeder” is advantaged in that it allows customers to place their documents into the tray face up. This is preferred because it is the normal way that customers read, prepare and handle multi page documents. It also allows the customer to observe how each sheet is to be treated as it enters the scanner. In the event that they observe a document beginning to be damaged or otherwise improperly fed, the operator may be able to intervene and correct a problem before it happens or before it has become more serious. In a bottom feeder, the operator must take the extra step to turn their documents over when placing them into the stack and they cannot as easily observe or intervene with sheets as they are fed from the bottom of the stack. In addition, feeding from the top of the stack is generally proven to be of higher reliability than feeding from the bottom of a stack. This is primarily due to the fact that each sheet in a top feeder has the same drag loads to overcome in order to advance it into the paper transport. In bottom feeding devices these drag forces are variable and dependent on how much stack resides above the sheet being fed. Each sheet being fed from beneath a stack must overcome the added drag forces incurred because of the weight of those sheets above it. This drives another key benefit of the top feeding approach which is capacity. Since top feeders do not have to contend with the weight of the stack, it is much easier to design top feeding systems using an elevating table with high stack capacities. Within the industry, top feeding devices are commonly delivered with stack capacities of 250, 500 or even 1,000 sheets while nearly all bottom feeding devices are limited to capacities of 50 to 150 sheets because of the stack drag force problem.
Another key benefit to the C or rotary design is in the ergonomic placement of the trays for in feed and exit. In the most ergonomic configurations, the C shape designs place the in-feed tray at a position close to the table or desk surface and the exit tray above it with the C shape paper path between them, such as shown in FIG. 1, for example. It is also preferred that both of these trays are oriented with both trays facing the seated operator. This configuration allows for optimum interaction with the feed and exit trays with minimal reach between them to load and unload documents. While a C design can also be offered with the in feed tray on top and the exit tray at the bottom, the preferred design places the in feed tray close to the desk surface since most scanner interventions occur in the in-feed tray. By configuring this tray closer to a table top surface, it minimizes the lifting of the arms and hands to elevated positions in order to perform the scanning operations. Performing repetitive operations with the hands well above the desk surface has been proven to increase operator fatigue, discomfort and injuries to the neck and shoulders. In some scanner designs the in feed and exit trays are oriented in a sideways arrangement. This creates an awkward process for loading and unloading the documents.
In addition to the ergonomic benefits described for operating the scanner, a C or rotary design has the ability to provide optimal access to the entire paper path length when it must be opened up for jam clearance and or maintenance. In the typical C or Rotary design, the entire paper path can be opened or exposed by unlatching the pod and hinging it upward. When offered with this path oriented to face the seated operator, this arrangement offers excellent visual and manual access to the paper path. In some scanners of different configurations, the operator must open and close several sections of the paper path in order to gain visual and manual access and some of these are not easily accessible from a seated position.
In summary, a forward facing C shaped transport with the in-feed tray close to table height and the exit tray above it, which opens up through one hinge affords an optimal design for feeding reliability, capacity, desk space and ergonomics for operation and maintenance.
FIG. 4 shows a typical flatbed scanner. In a flatbed scanner, a single document 34 is placed face down onto a transparent glass 40. The document is held flat to the glass by a pad 36 that is secured to the underside of cover 38. Camera 30 is moved linearly along shaft 32 by a motor drive system (not shown) to image the document. Cover 38 is typically mounted to a scanner main body 31 with one or more hinges 42 that allow the cover to be rotated open in a direction 35 for document placement. Hinges 42 typically include sliding members 44 that are free to move in vertical slots 46 in the main body. This allows the cover to fully seat against thick or irregularly shaped documents or other items. Because they are not restricted by a narrow document transport path, flatbed scanners are able to scan documents and items not able to be transported through a sheet fed scanner, such as books, thick documents, and three-dimensional objects. In production scanning applications, the majority of all documents are able to be fed using a sheet fed scanner and this is far more productive than using a flat bed. However, some “exception” documents, such as those of irregular dimensions, are encountered that require the use of a flatbed type scanner. It is therefore desirable to create a product design that can optimize both of these capabilities into one device while maintaining the key advantages of each.
Product solutions currently exist that have some, but not all of the desired benefits of a C-shaped sheet fed scanner and a flatbed scanner in a compact size. One common method is to tether a flatbed scanner to a C-shaped sheet fed scanner. This method requires two separate devices and occupies a significant amount of desk space. FIG. 5 shows one such combination in which flatbed scanner 44 is connected to sheet fed scanner 42 by tether cable 46. The cable provides an electronic digital communication medium between the scanners.
FIG. 6 shows another scanning system that combines a straight-through sheet fed scanner with a flatbed scanner. In this case, straight through sheet fed scanner 506, with input tray 502 and output tray 504, is mounted onto cover 510 of flatbed scanner 508. Cover 510 pivots about a hinge axis 512 to provide document access to the flatbed. This has the disadvantages of the straight through sheet fed scanner and has the ergonomic issue of requiring a human operator to lift a heavy scanner in order to access the flatbed for document placement.
In another configuration, a rotary scanner is placed atop a flatbed design. FIG. 7 depicts this approach in which C-shaped sheet fed scanner 162 is positioned above flatbed scanner 168. Sheet fed output tray 164 serves as a cover to flatbed 168 and is opened by rotating about the horizontal hinge axis 163 in direction 165. Sheet fed input tray 166 extends above the flatbed and must be moved in direction 169 before the flatbed cover 164 can be opened. This is because the operating position of the input tray blocks the movement of the output tray as it is opened in direction 165. In this design the ergonomic access to the input and output trays is suboptimum because they are loaded sideways and are elevated substantially from the desktop surface. The portion of this figure that is facing the viewer is deemed the front of the scanner, thus, the flatbed scanner is facing the front of the scanner apparatus because its cover 164 opens toward the front, while the output 164 and input 166 trays are facing a lateral side of the scanner because documents enter and exit the scanner in directions away from and toward that side, which is the right side of the scanner in FIG. 7.